double buffered video for fast loops

src/Video/VideoAV1.cs

@@ -3,10 +3,13 @@ using System.IO;
 
 namespace MoonWorks.Video
 {
-	public unsafe class VideoAV1 : IDisposable
+	public unsafe class VideoAV1
 	{
-		public IntPtr Handle => handle;
-		IntPtr handle;
+		public string Filename { get; }
+
+		// "double buffering" so we can loop without a stutter
+		internal VideoAV1Stream StreamA { get; }
+		internal VideoAV1Stream StreamB { get; }
 
 		public int Width => width;
 		public int Height => height;
@@ -19,8 +22,6 @@ namespace MoonWorks.Video
 		private int height;
 		private Dav1dfile.PixelLayout pixelLayout;
 
-		bool IsDisposed;
-
 		public VideoAV1(string filename, double framesPerSecond)
 		{
 			if (!File.Exists(filename))
@@ -28,12 +29,13 @@ namespace MoonWorks.Video
 				throw new ArgumentException("Video file not found!");
 			}
 
-			if (Dav1dfile.df_fopen(filename, out handle) == 0)
+			if (Dav1dfile.df_fopen(filename, out var handle) == 0)
 			{
 				throw new Exception("Failed to open video file!");
 			}
 
-			Dav1dfile.df_videoinfo(Handle, out width, out height, out pixelLayout);
+			Dav1dfile.df_videoinfo(handle, out width, out height, out pixelLayout);
+			Dav1dfile.df_close(handle);
 
 			if (pixelLayout == Dav1dfile.PixelLayout.I420)
 			{
@@ -56,34 +58,11 @@ namespace MoonWorks.Video
 			}
 
 			FramesPerSecond = framesPerSecond;
-		}
 
-		protected virtual void Dispose(bool disposing)
-		{
-			if (!IsDisposed)
-			{
-				if (disposing)
-				{
-					// dispose managed state (managed objects)
-				}
+			Filename = filename;
 
-				// free unmanaged resources (unmanaged objects)
-				Dav1dfile.df_close(Handle);
-
-				IsDisposed = true;
-			}
-		}
-
-		~VideoAV1()
-		{
-			Dispose(disposing: false);
-		}
-
-		public void Dispose()
-		{
-			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
-			Dispose(disposing: true);
-			GC.SuppressFinalize(this);
+			StreamA = new VideoAV1Stream(this);
+			StreamB = new VideoAV1Stream(this);
 		}
 	}
 }

src/Video/VideoAV1Stream.cs

@@ -0,0 +1,91 @@
+using System;
+
+namespace MoonWorks.Video
+{
+	internal class VideoAV1Stream
+	{
+		public IntPtr Handle => handle;
+		IntPtr handle;
+
+		public bool Ended => Dav1dfile.df_eos(Handle) == 1;
+
+		public IntPtr yDataHandle;
+		public IntPtr uDataHandle;
+		public IntPtr vDataHandle;
+		public uint yDataLength;
+		public uint uvDataLength;
+		public uint yStride;
+		public uint uvStride;
+
+		public bool FrameDataUpdated { get; private set; }
+
+		bool IsDisposed;
+
+		public VideoAV1Stream(VideoAV1 video)
+		{
+			if (Dav1dfile.df_fopen(video.Filename, out handle) == 0)
+			{
+				throw new Exception("Failed to open video file!");
+			}
+
+			Reset();
+		}
+
+		public void Reset()
+		{
+			lock (this)
+			{
+				Dav1dfile.df_reset(Handle);
+				ReadNextFrame();
+			}
+		}
+
+		public void ReadNextFrame()
+		{
+			lock (this)
+			{
+				if (Dav1dfile.df_readvideo(
+					Handle,
+					1,
+					out yDataHandle,
+					out uDataHandle,
+					out vDataHandle,
+					out yDataLength,
+					out uvDataLength,
+					out yStride,
+					out uvStride) == 1
+				) {
+					FrameDataUpdated = true;
+				}
+			}
+		}
+
+		protected virtual void Dispose(bool disposing)
+		{
+			if (!IsDisposed)
+			{
+				if (disposing)
+				{
+					// dispose managed state (managed objects)
+				}
+
+				// free unmanaged resources (unmanaged objects)
+				Dav1dfile.df_close(Handle);
+
+				IsDisposed = true;
+			}
+		}
+
+		~VideoAV1Stream()
+		{
+			Dispose(disposing: false);
+		}
+
+		public void Dispose()
+		{
+			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
+			Dispose(disposing: true);
+			GC.SuppressFinalize(this);
+		}
+	}
+}

src/Video/VideoPlayer.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Diagnostics;
+using System.Threading.Tasks;
 using System.Runtime.InteropServices;
 using MoonWorks.Audio;
 using MoonWorks.Graphics;
@@ -14,6 +15,7 @@ namespace MoonWorks.Video
 		public float PlaybackSpeed { get; set; } = 1;
 
 		private VideoAV1 Video = null;
+		private VideoAV1Stream CurrentStream = null;
 
 		private GraphicsDevice GraphicsDevice;
 		private Texture yTexture = null;
@@ -21,17 +23,6 @@ namespace MoonWorks.Video
 		private Texture vTexture = null;
 		private Sampler LinearSampler;
 
-		private object readLock = new object();
-		private bool frameDataUpdated;
-
-		private IntPtr yDataHandle;
-		private IntPtr uDataHandle;
-		private IntPtr vDataHandle;
-		private uint yDataLength;
-		private uint uvDataLength;
-		private uint yStride;
-		private uint uvStride;
-
 		private int currentFrame;
 
 		private Stopwatch timer;
@@ -152,7 +143,7 @@ namespace MoonWorks.Video
 			lastTimestamp = 0;
 			timeElapsed = 0;
 
-			Dav1dfile.df_reset(Video.Handle);
+			InitializeDav1dStream();
 
 			State = VideoState.Stopped;
 		}
@@ -176,28 +167,27 @@ namespace MoonWorks.Video
 			int thisFrame = ((int) (timeElapsed / (1000.0 / Video.FramesPerSecond)));
 			if (thisFrame > currentFrame)
 			{
-				if (frameDataUpdated)
+				if (CurrentStream.FrameDataUpdated)
 				{
 					UpdateRenderTexture();
 				}
 
 				currentFrame = thisFrame;
-				System.Threading.Tasks.Task.Run(ReadNextFrame);
+				Task.Run(CurrentStream.ReadNextFrame);
 			}
 
-			bool ended = Dav1dfile.df_eos(Video.Handle) == 1;
-			if (ended)
+			if (CurrentStream.Ended)
 			{
 				timer.Stop();
 				timer.Reset();
 
-				Dav1dfile.df_reset(Video.Handle);
+				Task.Run(CurrentStream.Reset);
 
 				if (Loop)
 				{
-					// Start over!
-					InitializeDav1dStream();
-
+					// Start over on the next stream!
+					CurrentStream = (CurrentStream == Video.StreamA) ? Video.StreamB : Video.StreamA;
+					currentFrame = -1;
 					timer.Start();
 				}
 				else
@@ -209,7 +199,7 @@ namespace MoonWorks.Video
 
 		private void UpdateRenderTexture()
 		{
-			lock (readLock)
+			lock (CurrentStream)
 			{
 				var commandBuffer = GraphicsDevice.AcquireCommandBuffer();
 
@@ -217,13 +207,13 @@ namespace MoonWorks.Video
 					yTexture,
 					uTexture,
 					vTexture,
-					yDataHandle,
-					uDataHandle,
-					vDataHandle,
-					yDataLength,
-					uvDataLength,
-					yStride,
-					uvStride
+					CurrentStream.yDataHandle,
+					CurrentStream.uDataHandle,
+					CurrentStream.vDataHandle,
+					CurrentStream.yDataLength,
+					CurrentStream.uvDataLength,
+					CurrentStream.yStride,
+					CurrentStream.uvStride
 				);
 
 				commandBuffer.BeginRenderPass(
@@ -269,28 +259,11 @@ namespace MoonWorks.Video
 
 		private void InitializeDav1dStream()
 		{
-			System.Threading.Tasks.Task.Run(ReadNextFrame);
-			currentFrame = -1;
-		}
+			Task.Run(Video.StreamA.Reset);
+			Task.Run(Video.StreamB.Reset);
 
-		private void ReadNextFrame()
-		{
-			lock (readLock)
-			{
-				if (Dav1dfile.df_readvideo(
-					Video.Handle,
-					1,
-					out yDataHandle,
-					out uDataHandle,
-					out vDataHandle,
-					out yDataLength,
-					out uvDataLength,
-					out yStride,
-					out uvStride) == 1
-				) {
-					frameDataUpdated = true;
-				}
-			}
+			CurrentStream = Video.StreamA;
+			currentFrame = -1;
 		}
 
 		protected virtual void Dispose(bool disposing)